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1. Field of the Invention
The present invention relates to improved method and apparatus for removing underwater tubular members such as the legs of abandoned marine platform jackets and like fixed platforms. The present invention also relates to the removal of underwater tubular members from a seabed using remote placement of explosive charges and an improved delivery system. Even more particularly, the present invention relates to improved method and apparatus for removing tubular members such as legs of marine jackets and like fixed platforms from the seabed by employing a specially configured delivery system that carries explosive charges that are to be placed inside of the hollow legs (or like tubular member) of an abandoned jacket or fixed platform, (e.g. oil well, oil production platform or the like).
2. General Background of the Invention
In the offshore oil and gas well drilling industry, there are a large number of fixed platforms that have been installed over the years in the fragile marine environment. These platforms typically involve the use of a structural steel frame or xe2x80x9cjacketxe2x80x9d that is comprised of a plurality of hollow tubular members, many of which are vertically oriented. In order to anchor the jacket to the seabed during installation, elongated hollow piling members are place through the vertical leg portions of the jacket and thrust downwardly into the seabed.
After a number of years of use, these offshore oil and gas well drilling platforms and production platforms can become obsolete. Under relevant laws, they are necessarily removed since they are a hazard to navigation. One of the methods of removing offshore oil and gas well drilling platforms and production platforms requires that the legs of the jacket or platform be severed below (e.g. 15 feet) the mud line. The remaining portion above the cut can be lifted from the seabed using a crane. The jacket or platform can be placed on a barge for later disposal at a suitable scrap yard or like site.
One of the problems that has faced the offshore oil and gas well drilling industry is the removal of obsolete or abandoned platforms without adversely effecting the surrounding marine environment. Typically, offshore marine environments are very delicate and should necessarily be minimally impacted by a method that is used to remove a fixed platform or production platform.
Another problem that faces a salvage company is excess expense and danger if a diver must cut the legs one at a time with an underwater cutting torch.
Prior U.S. Pat. Nos. 6,131,517 and 6,230,627 (each incorporated herein by reference) disclose apparatus and methods for removing abandoned offshore fixed platforms.
The present invention provides an improved delivery system for placing explosives that enable removal of an offshore fixed platform from the marine environment. In such a situation, the platform typically has a plurality of legs that extend below the seabed, each leg or like tubular member being hollow and having a leg wall with an inside surface.
The method of the present invention first lowers the delivery apparatus of the present invention within a leg at a selected locale. A frame supports a plurality of explosive charges. The charges have curved portions that track the curvature of the platform leg at an area to be severed.
The explosive charges carried by the frame are remotely operated to move outwardly and engage the inside wall surface of the leg at a desired location. The wall of the leg is then severed by detonating the explosive charge that are supported with the frame.
These steps are repeated until all of the legs have been severed. The platform is then lifted from the seabed so that it can be placed on a transport barge for disposal at a fabrication yard, salvage yard, or scrap yard.
The present invention provides an improved and remotely operated delivery system for placing explosive charges in a pipe to be severed. The delivery system provides a method of placing an adjustable frame within the leg or pipe to be salvaged at the seabed area, the frame having multiple, curved charge carriers that are automatically movable from a remote locale between retracted and expanded positions.
As part of the method, the frame and its explosive charges are positioned next to the inside wall surface of the leg. The frame is expanded to the expanded position using a trigger mechanism that can be actuated from a location well above the charges.
The frame can be lowered or otherwise remotely delivered to a site that would ordinarily be inaccessible and then xe2x80x9ctriggeredxe2x80x9d to thrust each charge against the wall to be severed.